Yes, the presence or absence of a detector in the double-slit experiment can affect the outcome. The double-slit experiment is a fundamental experiment in quantum mechanics that demonstrates the wave-particle duality of particles, such as electrons or photons.
In the basic setup of the double-slit experiment, particles are directed toward a barrier with two small slits. Behind the barrier, a screen is placed to capture the particles that pass through the slits. When no detector is placed to determine which slit the particles go through, an interference pattern emerges on the screen, indicating that the particles exhibit wave-like behavior and interfere with each other.
However, if a detector is placed to determine which slit a particle passes through, the interference pattern disappears, and the particles behave more like particles than waves. The act of observing or measuring the path of a particle collapses its wavefunction, causing it to behave as a particle and exhibit a particle-like distribution on the screen. This is known as the "observer effect" or "measurement effect."
The key point is that the presence of a detector fundamentally changes the experimental setup. The act of detecting which slit the particle passes through introduces interaction with the particle, which disturbs its quantum state and collapses its wavefunction. This disturbance prevents the particle from interfering with itself and leads to a different outcome on the screen.
It's worth noting that recent developments in quantum experiments, such as weak measurements and delayed-choice experiments, have explored more nuanced aspects of the double-slit experiment. These experiments involve turning the detector on and off at different times during the particle's journey, leading to intriguing results that challenge our intuitive understanding of causality and the role of measurement in quantum mechanics.